Here's a genuinely new idea: Basecase's Layers for iPad mini ($45) is a protective option consisting of a hard plastic shell with a detachable, replaceable cover. One cover comes in the $45 package, while others can be purchased separately as LayersLite for $25 each, enabling you to separately choose the look of the front and back pieces. The shell is straightforward, offering better-than-average protection but omitting button coverage. There's also…